Two hundred and three patients with Crohn's disease seen at Kyushu University, Fukuoka University, and their affiliated centers from 1973 to 1988 were followed for 4.4 +/- 3.2 years (mean +/- SD), to evaluate the prognosis relative to life span and surgery. Cumulative survival rate and cumulative operation rate were calculated by the life table method. Cumulative survival rates 5 and 10 years after diagnosis were 98.9% and 98.9%, respectively; these figures were not different from the expected survival rates in the sex-and age-matched general population. Cumulative operation rates 5 and 10 years after the onset of symptoms were 16.2% and 39.1%, respectively, In a second study, we investigated 419 patients with Crohn's disease, diagnosed at nine institutions from 1975 to 1990. The follow-up period was 6.3 +/- 3.9 years and the information was obtained from mailed questionnaires. Cumulative survival rates 5 and 10 years after diagnosis were 99.2% and 96.9%, respectively. Cumulative operation rates 5 and 10 years after the onset of symptoms were 30.3% and 70.8%, respectively. These results indicate that the prognosis of Japanese patients with Crohn's disease may be superior to that reported in Western countries.